Lemon Sheet Cake

Servings: 20
Prep Time 20 minutes
Cook Time 25 minutes
Cooling Time 1 hour 30 minutes
Total Time 45 minutes



  • 2 cups (248g) all-purpose flour
  • 1/4 cup (34g) cornstarch
  • 3/4 tsp baking powder
  • 1/2 tsp baking soda
  • 1/2 tsp salt
  • 1 1/2 cups (310g) granulated sugar
  • 2 Tbsp (10g) lemon zest
  • 3/4 cup (170g) unsalted butter, softened
  • 4 large eggs
  • 1 tsp vanilla extract
  • 1/2 cup (120ml) buttermilk
  • 1/2 cup (120g) sour cream
  • 2 Tbsp fresh lemon juice

Glaze and toppings

  • 3 1/4 cups (390g) powdered sugar
  • 1/3 cup (80ml) fresh lemon juice
  • Fresh strawberries, raspberries or blueberries for topping
  • Sliced lemons and mint leaves, for decoration (optional)


  1. Preheat oven to 350 degrees. Butter a rimmed 18 by 13-inch baking sheet (average size cookie sheet), dust with flour then shake out excess. 
  2. In a mixing bowl whisk together flour, cornstarch, baking powder, baking soda and salt for 20 seconds, set aside.
  3. In the bowl of an electric stand mixer fitted with the paddle attachment, mix together sugar and lemon zest for 30 seconds until fragrant and slightly yellow in appearance. 
  4. Add butter and whip mixture on medium speed until very pale and fluffy. Mix in eggs one at a time then blend in vanilla extract. 
  5. In a bowl or 2-cup liquid measuring cup whisk together buttermilk, sour cream and 2 Tbsp lemon juice. Add 1/3 of the flour mixture to the butter mixture and mix on low speed just until combined then add in 1/2 of the buttermilk mixture and mix just until combined. 
  6. Repeat once more with flour and buttermilk then end by mixing in last 1/3 of the flour mixture just until combined. Scrape down sides and bottom of bowl with a rubber spatula and fold batter several times to ensure it's evenly incorporated. 
  7. Pour and spread batter evenly onto prepared baking sheet (it will seem thin but it should bake up nearly to the top). Bake 22 - 25 minutes until toothpick inserted into center comes out clean. Cool completely on a wire rack.
  8. In a mixing bowl whisk together powdered sugar and lemon juice until smooth (If needed you can add a little more powdered sugar to thicken or more lemon juice to thin). 
  9. Pour and spread glaze over cooled cake. Chill 20 minutes to help set glaze (it won't set fully but to get cleaner cuts you'll need it to set slightly). Top with berries, lemon slices and mint just before serving.